The present invention relates generally to biocompatible fasteners and more particularly to impermanent biocompatible fasteners.
Biocompatible fasteners have long been used to fasten together two or more biological materials on or within a patient. Examples of biocompatible fasteners include sutures, staples, surgical glues, tissue clips and orthopedic fixation devices, such as bone plates, screws and the like. For certain applications, such as where the biocompatible fastener is implanted within a patient and is needed therewithin for only a limited period of time, it is highly desirable that the biocompatible fastener be impermanent or capable of degrading over time so that an additional medical procedure not be required to remove the fastener from the patient. For this reason, many biocompatible fasteners now in use are made entirely out of materials that, over time, become chemically degraded within a patient and, ultimately, are fully metabolized and excreted by the patient. (Other biocompatible fasteners are made out of materials that the body needs and are not excreted.) Such impermanent biocompatible fasteners are typically referred to in the art as bioabsorbable fasteners and are made out of materials including, but not limited to, homopolymers and copolymers of glycolide, lactide, xcex5-caprolactone and p-dioxanone, copolymers of glycolide and trimethylene carbonate, as well as polyanhydrides and polyorthoesters. See Middleton et al., xe2x80x9cSynthetic Biodegradable Polymers as Medical Devices,xe2x80x9d Medical Plastics and Biomaterials (March 1998), the disclosure of which is incorporated herein by reference.
Gastroesphageal reflux disease (GERD) is a disorder in which the lower esophageal sphincter, which is located in a distal portion of the esophagus adjacent to the junction between the esophagus and the stomach, allows contents of the stomach, including gastric acid and bile, to reverse flow into the distal portion of the esophagus during digestion. Complications associated with GERD include heartburn, pulmonary disorders, chest pain, esophageal ulcers, esophagitis, Barrett""s esophagus, and esophageal carcinoma.
Although weight loss and/or prescription acid blockers are typically preferred treatment options for GERD, various surgical procedures have been devised to treat GERD where weight loss and/or prescription drugs are ineffective or impractical. In one surgical procedure, known as Nissen fundoplication, a portion of the gastric fundus of the stomach is wrapped around the esophagus and is secured thereto using one or more biocompatible fasteners, typically in the form of sutures, surgical staples or surgical two-part fasteners. The wrapped gastric fundus applies pressure to the esophagus in such a way as to eliminate the reverse flow of stomach contents into the esophagus.
One of the more commonly used fundoplication procedures requires abdominal or thoracic incisions through which the fundus wrapping and securing can be performed. Due to the highly invasive nature of such surgery, complications and morbidity occur in a significant percentage of cases. In addition, these procedures are time-consuming, often taking a number of hours to perform, and may leave disfiguring scars where the incisions were made.
More recently developed fundoplication procedures limit somewhat the necessity of making large surgical incisions by utilizing laparoscopic ports or percutaneous endoscopic gastrostomy. Although these procedures are less invasive than those involving large abdominal and thoracic incisions, they are still invasive and have certain risks associated therewith. For example, general anaesthesia, which entails well-known risks, is typically used during these procedures.
An even more recently developed fundoplication procedure is endoluminal fundoplication. In endoluminal fundoplication, a flexible endoscope is passed first through a patient""s mouth and then through the esophagus to locate an attachment site at the gastroesophageal junction. A tissue grasping device is then positioned at the distal end of the endoscope and is attached to the located attachment site. Next, a tissue displacement device is positioned at the distal end of the endoscope and is used to displace the findus of the stomach in such a way as to create an intussusception of the esophagus into the gastric lumen. A fastener delivery device is then used to secure the gastric fundus to the esophagus at a first location. The fastener delivery device is then used to place additional fasteners at a plurality of additional desired fastener locations, thus securing the gastric fundus entirely around the esophagus.
Examples of endoluminal fundoplication procedures are disclosed in U.S. Pat. No. 6,086,600, inventor Kortenbach, which issued Jul. 11, 2000, and in U.S. Pat. No. 6,113,609, inventor Adams, which issued Sep. 5, 2000, both of which are incorporated herein by reference.
In the aforementioned U.S. Pat. No. 6,113,609, there is disclosed a fundoplication fastener that is made entirely out of a bioabsorbable material. One problem that has been noted by the present inventors is that, whereas a fundoplication fastener need only be capable of securing the gastric fundus to the esophagus for the approximately three- to six-month period of time necessary for the gastric fundus and the esophagus to become fused to one another, a bioabsorbable fundoplication fastener typically will remain in place for approximately two years before chemical degradation results in its structural decay.
It is an object of the present invention to provide a novel biocompatible fastener.
Therefore, according to one aspect of the invention, there is provided a biocompatible fastener, said biocompatible fastener having a first portion and a second portion, said first portion being made out of a first bioabsorbable material, said first bioabsorbable material having a first degradation rate, said second portion being made out of a material selected from the group consisting of a non-bioabsorbable material and a second bioabsorbable material, said second bioabsorbable material having a second degradation rate, said second degradation rate being slower than said first degradation rate.
It is another object of the present invention to provide a novel impermanent biocompatible fastener.
Therefore, according to another aspect of the invention, there is provided a biocompatible fastener as described above wherein said first portion is positioned within said biocompatible fastener so that degradation of said first portion results in fragmentation of the biocompatible fastener.
It is still another object of the present invention to provide an impermanent biocompatible fastener that overcomes at least some of the shortcomings discussed above in connection with existing impermanent biocompatible fasteners.
Therefore, according to still another aspect of the invention, there is provided a biocompatible fastener that comprises, in a preferred embodiment, a male portion and a female portion. The male portion includes a first base member, the first base member being generally flat and oval. A pair of male members are mounted on the bottom surface of the first base member, each male member comprising a cylindrical post extending downwardly from the bottom surface of the first base member and a conical head disposed at the bottom end of the post. The female portion includes a second base member, the second base member being generally flat and oval. A pair of sleeves are mounted on the top surface of the second base member and extend upwardly therefrom. Each sleeve defines a bore adapted to receive a head from a corresponding male member and is provided with a pair of longitudinal slots that endow the sleeve with some radial flexibility to facilitate insertion of a head into the bore. In addition, each sleeve is provided with a sharp tip at its top end to facilitate insertion of the sleeve through biological tissue. A substantially circumferential flange is formed on the inside of each sleeve. The flange extends radially into the bore and is engageable with the head once the head has been inserted therepast so as to inhibit premature withdrawal of the head from the bore. Except for an outer coating on each of the two heads, the fastener is made entirely of a non-bioabsorbable material. By contrast, the outer coating of the heads is made of a bioabsorbable material having a desired degradation rate. The thickness of the outer coating is appropriately selected so that degradation of the outer coating after a desired period of time permits each head to be withdrawn past its flange.
Because the heads of the aforementioned fastener are not made entirely of a bioabsorbable material, but rather, are made of an inner core of a non-bioabsorbable material and an outer coating of a bioabsorbable material, the thickness of the bioabsorbable material is less than it would otherwise be in a corresponding head made entirely out of the bioabsorbable material. Consequently, because of its reduced thickness, the bioabsorbable material becomes fully hydrated more rapidly and, therefore, degrades more quickly in the present fastener than in a corresponding fastener made entirely out of bioabsorbable material. As a result, by selecting an appropriate bioabsorbable material and by dimensioning the fastener appropriately, the life-span of the fastener can be tailored to the healing time for the fastened biological material, e.g., three to six months for tissue subjected to a findoplication procedure.
As can readily be appreciated, instead of or in addition to making the heads out of an inner core of non-bioabsorbable material and an outer coating of bioabsorbable material, the flanges can be made out of an inner core of non-bioabsorbable material and an outer coating of bioabsorbable material. A variety of other modifications to the aforementioned fasteners are also possible.
The above-described fasteners are amenable to being mass-produced by conventional molding techniques.
For purposes of the present specification and claims, it is to be understood that certain directional terms used herein, such as xe2x80x9ctop,xe2x80x9d xe2x80x9cbottom,xe2x80x9d xe2x80x9cupwardly,xe2x80x9d xe2x80x9cdownwardly,xe2x80x9d and the like, when used to describe the fastener of the present invention, are relative terms dependent upon the fastener being situated in a particular orientation vis-à-vis the viewer at a particular point in time. As can readily be appreciated, if the orientation of the fastener is altered, such directional terms may also need to be altered correspondingly.
Additional objects, features, aspects and advantages of the present invention will be set forth, in part, in the description which follows and, in part, will be obvious from the description or may be learned by practice of the invention. In the description, reference is made to the accompanying drawings which form a part thereof and in which is shown by way of illustration specific embodiments for practicing the invention. These embodiments will be described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural changes may be made without departing from the scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is best defined by the appended claims.